package io.shmilyhe.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Base64 编码
 */
public class B64 {

    private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=".toCharArray();  
   /** 
     * data[]进行编码 
     * @param data 
     * @return 
     */  
    public static String encode(byte[] data) {  
        int start = 0;  
        int len = data.length;  
        StringBuffer buf = new StringBuffer(data.length * 3 / 2);  

        int end = len - 3;  
        int i = start;  
        int n = 0;  

        while (i <= end) {  
            int d = ((((int) data[i]) & 0x0ff) << 16)  
                    | ((((int) data[i + 1]) & 0x0ff) << 8)  
                    | (((int) data[i + 2]) & 0x0ff);  

            buf.append(legalChars[(d >> 18) & 63]);  
            buf.append(legalChars[(d >> 12) & 63]);  
            buf.append(legalChars[(d >> 6) & 63]);  
            buf.append(legalChars[d & 63]);  

            i += 3;  
            /* 
            if (n++ >= 14) {  
                n = 0;  
                buf.append(" ");  
            }  */
        }  

        if (i == start + len - 2) {  
            int d = ((((int) data[i]) & 0x0ff) << 16)  
                    | ((((int) data[i + 1]) & 255) << 8);  

            buf.append(legalChars[(d >> 18) & 63]);  
            buf.append(legalChars[(d >> 12) & 63]);  
            buf.append(legalChars[(d >> 6) & 63]);  
            buf.append(legalChars[64]);  
        } else if (i == start + len - 1) {  
            int d = (((int) data[i]) & 0x0ff) << 16;  

            buf.append(legalChars[(d >> 18) & 63]);  
            buf.append(legalChars[(d >> 12) & 63]);  
            buf.append(legalChars[64]); 
            buf.append(legalChars[64]); 
        }  

        return buf.toString();  
    }  

    private static int decode(char c) { 
        if (c >= 'A' && c <= 'Z')  
            return ((int) c) - 65;  
        else if (c >= 'a' && c <= 'z')  
            return ((int) c) - 97 + 26;  
        else if (c >= '0' && c <= '9')  
            return ((int) c) - 48 + 26 + 26;  
        else  
        {   
            if(c==legalChars[62])return 62;
            if(c==legalChars[63])return 63;
            if(c==legalChars[64])return 0;
            
            /*for(int i=0;i<65;i++){
                System.out.println(legalChars[i]+":"+i);
            }*/
            //System.out.println(legalChars[61]+":"+c);
            //这里应该把不合法的code 向上传递的，但是代码扫描说 涉嫌信息泄漏
            throw new RuntimeException("unexpected code: "); 

        }
            
    }  

    /** 
     * Decodes the given Base64 encoded String to a new byte array. The byte 
     * array holding the decoded data is returned. 
     */  

    public static byte[] decode(String s) {  

        ByteArrayOutputStream bos = new ByteArrayOutputStream();  
        try {  
            decode(s, bos);  
        } catch (IOException e) {  
            throw new RuntimeException();  
        }  
        byte[] decodedBytes = bos.toByteArray();  
        try {  
            bos.close();  
            bos = null;  
        } catch (IOException ex) {  
            System.err.println("Error while decoding BASE64: " + ex.toString());  
        }  
        return decodedBytes;  
    }  

    private static void decode(String s, OutputStream os) throws IOException {  
        int i = 0;  

        int len = s.length();  

        while (true) {  
            while (i < len && s.charAt(i) <= ' ')  
                i++;  

            if (i >= len)  
                break;  
            int b1=0;
            int b2=0;
            int b3=0;
            int b4=0;
            if(i<len){
                b1=(decode(s.charAt(i)) << 18) ;
            }
            if(i+1<len){
                b2=(decode(s.charAt(i + 1)) << 12) ;
            }
            if(i+2<len){
                b3= (decode(s.charAt(i + 2)) << 6);
            }
            if(i+3<len){
                b4= (decode(s.charAt(i + 3))); 
            }

            /*int tri = (decode(s.charAt(i)) << 18)  
                    + (decode(s.charAt(i + 1)) << 12)  
                    + (decode(s.charAt(i + 2)) << 6)  
                    + (decode(s.charAt(i + 3)));  */
            int tri=b1+b2+b3+b4;
            os.write((tri >> 16) & 255);  
            if (i+2>=len||s.charAt(i + 2) == '=')  
                break;  
            os.write((tri >> 8) & 255);  
            if (i+3>=len||s.charAt(i + 3) == '=')  
                break;  
            os.write(tri & 255);  

            i += 4;  
        }  
    }  
        
        public static void main(String[] agrs){
        	//String str ="Basic YWRtaW46YWRtaW4=";
        	//System.out.println(encode("最a国a中a人bi我c爱j！%$@r^&*()_".getBytes()));
        	//System.out.println(new String(decode("YWRtaW46YWRtaW4")));
        }


}
